This invention relates to resilient sign and guidepost, the construction and manufacture of such posts, and more particularly to the construction and manufacture of flexible roadway signs or guideposts. In another aspect the invention relates to flexible posts which are self-erecting in the event the post is accidentally hit or bent by a motor vehicle when the post is utilized in any environment wherein motor vehicles are present.
Motor vehicle traffic control, parking control and roadway control require the use of signs and markers as aids in solving the various problems associated with traffic safety. For many years, various attempts have been made to make roadway posts as well as other types of posts, marker devices and post supporting signs from the forgiving material such as flexible plastic materials. Not only should the posts be made of forgiving materials, for example one which yields in some manner when impacted by a motor vehicle in motion as distinguished from a rigid type device such as a steel post, but the forgiving traffic post should also have the ability to right itself due to the elasticity and resilience of the materials of construction along with the design of the post. In addition, these posts should be able to resist shear on impact thus avoidance of injury to people who may be travelling in motor vehicles which impact the posts. The importance of this type of resilient post has become apparent with increase in accidents involving sign posts and traffic lane markers which have been made of rigid materials that upon impact have snapped and penetrated spear-like into vehicles, in many cases causing death and severe injuries.
In more recent times, it has been found that a useful characteristic for such posts and markers is that these posts have the ability to withstand vehicle impact, without requiring subsequent replacement or without breaking or shearing from the base and becoming a free projectile. An attempt has been made to fulfill this need with various configurations of posts. However, the structure design of such posts must involve the consideration of two opposing structural features, i.e. the resilience required during dynamic conditions to permit the posts to non-destructively bend with vehicle impact and the longitudinal rigidity required during static conditions to withstand forces resulting as the post is driven into the ground.
Most commercially acceptable highway sign and marker posts continue to be made of T-shaped rigid steel construction. Such posts are relatively heavy and expensive and in highway usage such posts pose a substantial safety hazard when struck by vehicles. Substantial damage to the vehicle and personal safety of driver and passengers is compromised by the driver which loses control of the vehicle and in many cases the steel posts have punctured the vehicle causing direct injury to the passengers or driver. In the recent past, these posts have been made of low impact resistant plastic materials which have snapped off but are of such light weight that the posts cannot cause the type of damage or injury which has occurred using stronger steel devices. Other forms of utilized materials which will bend over, but which after impact are not reusable have been proposed. Yet another type of device has taken the form of spring supported cushioning pads or bumpers which are shock absorbent to a certain degree but again, are substantially destroyed by impacting vehicles.
In designing roadway marking or sign posts it is highly desirable for the posts to be constructed in a manner which provides for quick and simple installation and resiliency so that the post is able to withstand several impacts from bumpers of high speed vehicles without damaging or destroying the posts and without pulling the posts out of the ground. The ease and speed of installation is particularly important in view of the large number of marking posts used along the highways and expressways and the fact that frequently the installation of marking posts is performed when the installer is exposed to substantial motor vehicle traffic.
The resiliency is necessary in view of frequent high speeds associated with impacting motor vehicles and the stationary posts. In such cases, if the post does not bend it will likely shear off and will require replacement. Mere bendability, however, is not sufficient since each time a post has been bent it would have to straighten before it could again be functional. This could include high maintenance costs if manual straightening or treatment is required. Ideally, a post should have sufficient resiliency that the post will automatically assume its proper upright configuration after experiencing impact forces.
While resiliency is desirable, the resiliency presents a practical problem when installation of the post is considered. In the past when deformable plastics have been used as post material, installation has frequently required a pre-drilled hole or insertion of some support receptacle in the ground. Drilling the hole and/or implanting a receptacle in the ground followed by the subsequent positioning of the plastic post into the hole or receptacle is time consuming and not satisfactory. These multiple step installations have been required because previously known resilient posts have not withstood buckling force applied during attempts to drive the post into hard surfaces. Consequently, the same resilient properties which permit the non-destructive deformation upon impact causing the buckling of a post subjected to the driving force along its axis. The dual requirements of resiliency and rigidity utilizing spring devices and various elastomeric post construction have only been partially successful. While the foregoing problems have been long recognized and the use of plastic materials for posts has previously been suggested, the present invention utilizes the following different concepts to solve these prior problems.
The resilient sign and guidepost according to the invention is not subject to the limitations of these previously known devices but is a resilient device which bends sufficiently over on impact, allowing the vehicle to pass over the post thereafter the post resiliently returns to its normal use position. The post thus achieves the advantage of safety to people combined with an effective low cost because it remains usable and may not need to be immediately replaced with a new unit. Simplistic construction provides additional advantages along with ease of installation and relatively inexpensive manufacturing. In addition, it is desirable for the post to be installed in a manner by which the post may not be easily damaged or removed by a person walking along the roadway. The post should also be amenable to carrying reflective material, signs or other mounted informational features which cannot be easily scraped off or removed from the post by vandal or a motor vehicle impacting the post.
U.S. Pat. No. 3,875,720 discloses an approach to the problem of providing elasticity to a post that can be driven. A post is formed by a bundle of flexible rods that are clamped together to obtain a desired rigid property required doing static installation of the post. Deformation of posts during dynamic conditions is permitted by deflection of the various rods away from the central axis of the post structure. Economic factors appear to have impeded utilization of such structure despite the growing need for such a post.
U.S. Pat. No. 4,522,530 provides a self-erecting roadway marking post through utilization of an extruded resilient plastic material tube with a lower end portion of the tube carrying a set of spring fingers which project outwardly from the tube to engage the ground surrounding a hole which receives the lower end portion of the tube. Another self-erecting roadway marking post is presented by U.S. Pat. No. 4,343,567 wherein a metal anchor tube is driven into the ground which defines a cavity for receiving a lower end portion of an elongated cylindrical flexible marking tube. A resilient plastic reinforcing tube is inserted within a long marking tube so that it bends with the marking tube and aids in returning the marking tube to its normal upright position after being hit. Both of these self-erecting roadway marking posts utilize some sort of separately installed base anchor mechanism and/or spring mechanism to assist the elongated flexible tube or post to be self-erecting.